Arc chute for an air circuit breaker

ABSTRACT

Discloses an exhaust cooler for the arcing products leaving the arc chute of an electric circuit breaker. The cooler has four open sides. Through one of these sides the arcing products enter the cooler, and through the other three sides the arcing products exhaust after passing through the cooler. The cooler comprises a stack of corrugated metal sheets that allow the arcing products to pass between the sheets along the length of the corrugations and out one of said open exhaust sides of the cooler. The corrugated sheets are perforated to permit arcing products also to pass transversely of the length of the corrugations and out the remaining two open exhaust sides of the cooler.

United States Patent [72] Inventors Gerhard Frind Glenolden, Pa.; Rudolf Hunziker, Collingswood, N .J Richard M. Korte, Media, Pa. [21] Applv No. 786,126 [22] Filed Dec. 33, 1968 [45] Patented Jan. 12,1971 73] Assignee General Electric Company a corporation of New York [54] ARC CHUTE FOR AN AIR CIRCUIT BREAKER 5 Claims, 7 Drawing Figs.

521 US. Cl 200/144, 200/ 147 [51] Int. Cl H0lh 9/34 [50] Field of Search 200/144, 148.3, 147, 147B [5 6] References Cited UNITED STATES PATENTS 2,272,214 2/1942 Linde ZOO/148(3) 2,293,513 8/1942 Linde ZOO/144 2,408,352 9/1946 Titus ZOO/144 3,033,961 5/1962 Carter ZOO/147B FOREIGN PATENTS 715,121 9/1954 Great Britain 200/147 Primary Examiner-Robert S. Macon Att0rneysJ. Wesley l-laubner, William Freedman, Frank L.

Neuhauser, Oscar B. Waddell and Melvin M. Goldenberg ABSTRACT: Discloses an exhaust cooler for the arcing products leaving the arc chute of an electric circuit breaker. The cooler has four open sides. Through one ofthese sides the arcing products enter the cooler, and through the other three sides the arcing products exhaust after passing through the cooler. The cooler comprises a stack of corrugated metal sheets that allow the arcing products to pass between the sheets along the length of the corrugations and out one of said open exhaust sides of the cooler. The corrugated sheets are perforated to permit arcing products also to pass transversely of the length of the corrugations and out the remaining two open exhaust sides of the cooler.

ARC CHUTE FOR AN AIR CIRCUIT BREAKER This invention relates to an arc chute for an air circuit breaker and, more particularly, relates to means for cooling the hot gases emitted from the exhaust of the arc chute during circuit interruption and for reducing the possibility of a flashover through these exhaust gases.

in the type of arc chute that we are concerned with, the electric are established upon contact-separation is driven into the arc chute, where it is lengthened and cooled to facilitate arc-extinction. An exhaust passage is provided at one end of the arc chute to receive the hot, gaseous arcing products developed during the interrupting operation. To cool the hot arcing products flowing through the exhaust passage and to reduce the chance for a flashover outside the chute through the hot outstreaming arcing products, it has been customary to provide an exhaust cooler through which the arcing products are passed before they leave the chute. The arcing products leaving the cooler, being at a lower temperature, have a higher dielectric strength and are therefore less likely to induce a flash over between adjacent electrically-stressed parts of the circuit breaker. I

A problem encountered with prior exhaust coolers is that when they have been made effective enough to provide the desired cooling action, they have presented an excessive amount of flow impedance to the outstreaming arcing products. This excessive flow impedance can cause so much back pressure to build up ahead of the are that the arc is unable to move deeply into the chute, as is desired for are extinction, or is unduly retarded in so moving.

An object of the present invention is to provide, for an arc chute, an exhaust cooler that is capable of effecting the desired cooling of arcing products without introducing such high flow impedance as to impair the ability of the arc to move 2 at one end between the sidewalls through which hot arcing products leave the chute. An exhaust cooler is mounted ad jacent the exhaust passage so that arcing products pass therethrough upon leaving said are chute. The exhaust cooler comprises a plurality of corrugated metal sheets, each sheet extending transversely of said sidewalls and including corrugations having their respective length dimensions extending in generally the same direction as the direction followed by the arcing products as they enter said cooler from said exhaust passage. The exhaust cooler is open at a side opposite said exhaust passage so that arcing products may pass along the length of said corrugations and exhaust through said opposite side. The corrugated sheets have many perforations therein that interconnect the spaces bounded by the corrugations in a given sheet to allow arcing products to pass between said spaces via paths extending transversely of the length of the corrugations. The exhaust cooler has transverse sides extending generally parallel to the length dimension of said corrugations. These transverse sides are an open construction to allow arcing products to exhaust therethrough after having traversed the corrugations by paths extending transversely of the length thereof via said perforations.

For a better understanding of the invention reference may be had to the following description taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a side elevational view partly in section of an air circuit breaker embodying one form of our invention.

FIG. 2 is a sectional view along the line 2-2 of FIG. 1.

FIG. 3 is an enlarged view of a portion of F IG. 2.

FIG. 4 is a sectional view along the line 44 of FIG. 3 and particularly showing the exhaust cooler.

FIG. 5 is an exploded perspective view of some of the components of the exhaust cooler of FIG. 4.

FIG. 6 illustrates a modified embodiment of the invention.

FIG. 7 illustrates another modified embodiment.

Referring now to FlG. l, the circuit breaker illustrated therein is an air circuit breaker of the magnetic blowout type. It comprises a pair of relatively movable contacts 1 and 2 for establishing an arc and an arc chute 7 into which the arc is driven in order to extinguish it. Contact l is a fixed contact, and contact 2 is a movable contact that is pivotally mounted at 3 on one of the circuit breaker studs 6 and is operated by means of reciprocally-movable insulating rod 4. The insulating rod 4 is suitably connected to an actuating mechanism (not shown) for operating the movable contact between closed and open-circuit positions. The contacts 1 and 2 are electrically connected to the lower ends of the breaker lead-in studs 5 and 6, which also serve as the breaker terminals. Accordingly, when the breaker is connected in a power circuit and the contacts l and 2 are separated, an arc is established between the contacts.

For extinguishing this arc, the arc chute 7 is mounted with respect to the contact structure so as to directly receive the arc. The are is driven into the arc chute along metal runners 8 and 9' by a magnetic blowout field produced by blowout coils 8 and 9. The contacts, the runners, and the magnetic blowout structures can assume any suitable form; and since their details comprise no part of the present invention, a brief description is considered sufficient. The magnetic blowout coils 8 are electrically connected to the conductive stud 5 and to the conductive arc runners 8' so that the arc current (as the arc travels along the runners) flows through the blowout coils to create a portion of the magnetic field for driving the arc into the chute.

Normally, the current through the closed breaker is carried by the main contacts 1' and 2; but upon separation of these contacts during opening, the current is shunted to the arcing contacts 1, 2. When the contacts 1, 2 separate to establish the arc, the upper arc terminal moves quickly on to the upper runner 8' and toward the interior of the chute. When the movable contact 2 approaches the intermediate position of FIG. '2, the lower terminal of the arc transfers to the runner 9. This causes the lower blowout coil 9' to be connected in series with the arc since the coil 9 is electrically connected as indicated at 9" between the stud 6 and the lower arc runner 9'. Thus, the blowout coils are energized at an early stage to drive the arc into the chute in a well-known manner. Although not shown, the blowout coils are provided with pole pieces at the outer sides of the chute to provide a magnetic field of the most efficient configuration for moving the are into the chute.

The arc chute further comprises a pair of sidewalls 10 and 11 of appropriate arc-resistant insulating material. These sidewalls are clamped together in spaced-apart relationship by suitable means (not shown). Each sidewall preferably comprises fins 10' projecting toward the other sidewall and arranged to mutually interleave with corresponding projecting fins on the other sidewall, thereby forming a zigzag path as viewed from the entrance end of the chute. As shown in FIG. 2, the fins taper toward the entrance of the chute and thereby provide a throat portion through which the arc must first pass before entering the zigzag passage between fins 10'. Generally speaking, this construction of the contacts, the runners, the blowout structure and the arc chute is of the type disclosed in U.S. Pat. No. 2,293,5 l3-Linde, assigned to the assignee of the present invention.

As the arc moves into the arc chute, it is stretched around the edges of the fins 10 and is forced into intimate engagement with the surfaces of the fins and sidewalls as it assumes an increasingly sinuous configuration. This causes gases to be evolved from the fins and sidewalls, and these gases together with other arcing products are heated by the arc and expelled from the chute through an exhaust opening 30 at the rear of the arc chute in the direction of the arrows 34.

For cooling these hot arcing products, we provide an exhaust cooler 35 mounted adjacent the exhaust opening 30. This exhaust cooler 35 is of a rectangular cross section as viewed in FIGS. 2 and 3. For reasons which will soon be explained, all four sides of the exhaust cooler are open to the maximum practical extent. The hot gaseous arcing products leaving the arc chute through exhaust opening enter the exhaust cooler through one of its open sides 36, which is located immediately adjacent the exhaust opening 3t). These arcing products flow through the exhaust cooler, exiting therefrom both through the opposite side 38 of the cooler (as indicated by arrows 60) and through the open transverse sides 40 and 42 (as indicated by the arrows 46 and 47).

For mounting the exhaust cooler in the illustrated position, the sides 40 and 42 thereof are provided with extensions secured to the sidewalls 10 and 11 of the arc chute by suitable fastening means (not shown).

The exhaust cooler 35 comprises a plurality of corrugated metal sheets 50 which are stacked vertically along substantially the entire vertical dimension of the arc chutes exhaust opening 30. These sheets 50 extend transversely of the sidewalls 10 and 11. Each of these corrugated metal sheets 50 has alternate ridges and furrows, or corrugations, having their length dimensions extending in generally the same direction as the direction (34) followed by the arcing products as they enter the exhaust cooler. Each of these metal sheets 50 also contains a large number of perforations 53 that afford free communication between the spaces bounded by the corrugations of a given sheet 50.

Between adjacent pairs of corrugated metal sheets 50 are located planar metal sheets 55, each having a large number of perforations 56. These perforations 56 afford free communication between the spaces bounded by the corrugations on opposite sides of each planar sheet 55.

The perforated sheets 50 and 55 are made of a metal having a relatively high thermal conductivity, such as copper or aluminum. This high conductivity contributes to their cooling ability.

The gaseous arcing products enter the cooler 35 via paths such as depicted at 34. Some of the arcing products flow through the cooler along the length of the corrugations to the opposite side 38 of the cooler, exhausting from the cooler via paths such as 6t). As previously mentioned, other portions of the arcing products flow through the cooler transversely of the flow path 60. This latter gas flows through the holes 53 in the corrugated metal plates 55. Since there are a great number of holes in metal plates 55 and these holes are generally made as large as possible, the impedance to such transverse flow is kept quite low.

The holes in the metal plates 50 and 55 materially contribute to the effectiveness of the cooling action since they produce a high degree of turbulence in the gases passing through the cooler; and this turbulence accelerates heat transfer from the gases to the adjacent metal.

As was pointed out hereinabove, a problem that has heretofore been encountered with exhaust coolers is that those designs which have extensive enough cooling surfaces to perform an effective cooling job have presented an excessive amount of flow impedance to the gases passing therethrough. This excessive flow impedance can cause so much back pressure to build up ahead of the are as to block or harmfully retard movement of the are along the arc runners 8, 9' and into the zigzag space between the fins 10. The flow impedance of our exhaust cooler is maintained very low, primarily because we allow the exhaust gases to vent through three sides of the cooler, instead of only one side as is customary. in this respect, we do not confine the arcing products to the straight-through paths but allow them to vent via the transversely extending paths 46 and 47 as well. This transverse flow is made possible not only by the open transverse sides 40 and 42 of the arc cooler but also by the many holes 53 in the corrugated metal plates 50 that permit gas to flow transversely of the corrugations toward the open transverse sides ltl and 42..

The holes 56 in the planar metal plates 55 also contribute to reduced flow impedance by allowing some of the gas to flow through the planar plates, thus helping to equalize the flow through the spaces in adjacent corrugated plates Stl.

The stack of perforated sheets 50 and 55 is divided into a plurality of groups by planar plates 61 of insulating material located at spaced intervals along the stack length. These insulating plates 6H extend parallel to the planar metal sheets 55. in a preferred embodiment, the stack of metal sheets between each pair of insulating plates 61 contains'three corrugated sheets 50 and two planar metal sheets' 55. The insulating plates 6ll are imperforate so as to provide good electrical isolation between the short stacks of metal plate's'located at opposite sides of the insulating plates. As'can be seen in FIG. 4-, the insulating plates 61 are slightly larger than the metal sheets 54 and 55 and therefore have edge portions 62 which project out beyond the edges of the metal sheets 50, 55.

The insulating plates aremadeo'fan insulating material, such as a suitable fiber, which will nbtcarbonize and is capable of evolving gases when exposed to the hot arcing products. When the hot arcing products enter the arc cooler they first encounter the overhanging edges 62 of the fiber plates, and the gases evolved therefrom help to cool the arcing products before they reach the metal sheets 50, 55. A primary function of the insulating plates 61 is to electrically isolate sections of the metal stack from each other so as to eliminate any continuous metal path along the length of the stack. Another important function of the insulating plates is to prevent a fiashover from occurring along an outer surface of the overall metal-sheet stack. in this connection, the overhang'of the insulating plates beyond the edges of the metal sheets increases the creepage distance available -to withstand a breakdown along the outer surface of the stack and also helps to isolate the gas entering and leaving one group of metal sheets 50, 55 from that entering and leaving anadjacent group.

Although the preferred embodiment of our'inv'ntion shown in FIGS. 3-5 employs perforated sheets such as 50 and 55 for cooling, it is to be understood that the invention in its broader aspect coriiprehends the use of other types of perforated, or porous, cooling structure. For example, we can employ relatively coarse metal screens such as shown at and 71 in F IG. 6 instead of the perforated sheets 50 and 55. As another example we can utilize corrugated screen members 75 stacked across the main flow path 34 from the arc chute, as is illustrated in F IG. 7. Whatever type of porous cooling structure is used, however, should be sufficiently porous and open as to allow the gases to follow transversely-extending paths, such as 46 and 47 in FIGS. 3 and 7, as well as the generally straightthrough paths 60. in all forms of the invention, it is important that the exhaust cooler be freely open at its transverse sides 40 and 42 (FIG. 3) as well as at its back side'38 to permit the gases to be exhausted through all three of these sides of the cooler. This three-directional exhausting plays a very important role in limiting the flow impedance of the cooler to the desired low level. It is to be further understood that in each of the modified embodiments, the cooling structure comprises a plurality of units separated by planar plates of insulating material corresponding to the plates 61 of FIGS. 3 and4.

The embodiment shown in FIGS. '3 and 4 is especially advantageous because it lends itself to simple and inexpensive manufacture and assembly and has a high degree of dimensional stability. It is a simple matter to corrugate the sheets 50 and to stack the parts to form the desired chute, No welding or other special fastening operations are needed to form the assembly of FlGS. 3 and 4.

.While we have shown and described particular embodiments of the inventiomit will be obvious those skilled in the art that various changes and modifications may be made without departing from the invention in its broader aspects; and we, therefore, intend in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of our invention.

We claim:

ll. An electric air circuit breaker comprising:

a. means for establishing an arc;

b. an arc chute into which said are is driven comprising spacedapart insulating sidewalls and arc-extinguishing means disposed in the space between said sidewalls;

c. said are chute having an exhaust passage at one end between said sidewalls through which hot arcing products leave said arc chute;

d. an exhaust cooler mounted adjacent said exhaust passage through which said arcing products pass upon leaving said are chute;

e. said exhaust coole. comprising;

1. a plurality of stacked corrugated metal sheets, each sheet extending transversely of said sidewalls and including corrugations having their respective length dimensions extending in generally the same direction as the direction followed by the arcing products as they enter said cooler from said exhaust passage,

2. said exhaust cooler being open at a side opposite said exhaust passage so that arcing products may pass along the length of said corrugations and exhaust through said opposite side,

3. said sheets having many perforations therein that interconnect the spaces bounded by the corrugations in a given sheet to allow arcing products to passbetwecn said spaces via paths extending transversely of the length of the corrugations,

f. said exhaust cooler having a pair of transverse outer sides extending generally parallel to the length dimension of said corrugations; and

g. said exhaust cooler being open at said transverse sides to allow arcing products to exhaust therethrough after having traversed the corrugations by paths extending transversely of the length thereof via said perforations.

2. The circuit breaker of claim 1 in which said exhaust cooler further comprises: plates of insulating material disposed between adjacent groups of said stacked metal sheets to electrically isolate adjacent groups from each other, thereby inhibiting a flashover along the length of said stack.

3. The circuit breaker of claim 1 or claim 2 in which said exhaust cooler further comprises additional metal sheets of generally planar form disposed between adjacent ones of said corrugated metal sheets, said additional metal sheets having perforations therein that afford communication between the spaces bounded by the corrugations at opposite sides of said additional metal sheets.

4. An electric air circuit breaker comprising:

a. means for establishing an arc;

b. an arc chute into which said are is driven comprising spaced-apart insulating sidewalls and arc-extinguishing means disposed in the space between said sidewalls;

said are chute having an exhaust passage at one end between said sidewalls through which hot arcing products leave said are chute;

. an exhaust cooler mounted adjacent said passage through which said arcing products pass upon leaving said are chute;

e. said exhaust cooler comprising porous metal structure containing passages therethrough that allow said arcing products to flow freely through the porous structure in a first direction that is generally the same direction as that followed by the arcing products as they enter said cooler from said exhaust passage and additional passages therethrough that allow said arcing products to flow freely through said cooling structure transversely of said first direction;

f. said exhaust cooler having a pair of transverse outer sides extending generally parallel to said first direction; and

said exhaust cooler being open at said transverse sides to allow arcing products to exhaust therethrough after flowing through cooling structure transversely of said first direction.

5. The circuit breaker of claim 4 in which said exhaust cooler further comprises a plurality of said porous structures stacked along said'exhaust opening and plates of insulating material disposed between adjacent porous structures to electrically isolate adjacent structures from each other, thereby inhibiting a flashover along the length of said stack. 

1. An electric air circuit breaker comprising: a. means for establishing an arc; b. an arc chute into which said arc is driven comprising spacedapart insulating sidewalls and arc-extinguishing means disposed in the space between said sidewalls; c. said arc chute having an exhaust passage at one end between said sidewalls through which hot arcing products leave said arc chute; d. an exhaust cooler mounted adjacent said exhaust passage through which said arcing products pass upon leaving said arc chute; e. said exhaust cooler comprising;
 1. a plurality of stacked corrugated metal sheets, each sheet extending transversely of said sidewalls and including corrugations having their respective length dimensions extending in generally the same direction as the direction followed by the arcing products as they enter said cooler from said exhaust passage,
 2. said exhaust cooler being open at a side opposite said exhaust passage so that arcing products may pass along the length of said corrugations and exhaust through said opposite side,
 3. said sheets having many perforations therein that interconnect the spaces bounded by the corrugations in a given sheet to allow arcing products to pass between said spaces via paths extending transversely of the length of the corrugations, f. said exhaust cooler having a pair of transverse outer sides extending generally parallel to the length dimension of said corrugations; and g. said exhaust cooler being open at said transverse sides to allow arcing products to exhaust therethrough after having traversed the corrugations by paths extending transversely of the length thereof via said perforations.
 2. said exhaust cooler being open at a side opposite said exhaust passage so that arcing products may pass along the length of said corrugations and exhaust through said opposite side,
 2. The circuit breaker of claim 1 in which said exhaust coolEr further comprises: plates of insulating material disposed between adjacent groups of said stacked metal sheets to electrically isolate adjacent groups from each other, thereby inhibiting a flashover along the length of said stack.
 3. said sheets having many perforations therein that interconnect the spaces bounded by the corrugations in a given sheet to allow arcing products to pass between said spaces via paths extending transversely of the length of the corrugations, f. said exhaust cooler having a pair of transverse outer sides extending generally parallel to the length dimension of said corrugations; and g. said exhaust cooler being open at said transverse sides to allow arcing products to exhaust therethrough after having traversed the corrugations by paths extending transversely of the length thereof via said perforations.
 3. The circuit breaker of claim 1 or claim 2 in which said exhaust cooler further comprises additional metal sheets of generally planar form disposed between adjacent ones of said corrugated metal sheets, said additional metal sheets having perforations therein that afford communication between the spaces bounded by the corrugations at opposite sides of said additional metal sheets.
 4. An electric air circuit breaker comprising: a. means for establishing an arc; b. an arc chute into which said arc is driven comprising spaced-apart insulating sidewalls and arc-extinguishing means disposed in the space between said sidewalls; c. said arc chute having an exhaust passage at one end between said sidewalls through which hot arcing products leave said arc chute; d. an exhaust cooler mounted adjacent said passage through which said arcing products pass upon leaving said arc chute; e. said exhaust cooler comprising porous metal structure containing passages therethrough that allow said arcing products to flow freely through the porous structure in a first direction that is generally the same direction as that followed by the arcing products as they enter said cooler from said exhaust passage and additional passages therethrough that allow said arcing products to flow freely through said cooling structure transversely of said first direction; f. said exhaust cooler having a pair of transverse outer sides extending generally parallel to said first direction; and g. said exhaust cooler being open at said transverse sides to allow arcing products to exhaust therethrough after flowing through cooling structure transversely of said first direction.
 5. The circuit breaker of claim 4 in which said exhaust cooler further comprises a plurality of said porous structures stacked along said exhaust opening and plates of insulating material disposed between adjacent porous structures to electrically isolate adjacent structures from each other, thereby inhibiting a flashover along the length of said stack. 